title: Nanoparticles in photodynamic therapy: an emerging paradigm.
abstract: Photodynamic therapy (PDT) has emerged as one of the important therapeutic options in management of cancer and other diseases [M. Triesscheijn, P. Baas, J.H. Schellens, F.A. Stewart, Photodynamic therapy in oncology, Oncologist 11 (2006) 1034-1044]. Most photosensitizers are highly hydrophobic and require delivery systems. Previous classification of delivery systems was based on presence or absence of a targeting molecule on the surface [Y.N. Konan, R. Gurny, E. Allemann, State of the art in the delivery of photosensitizers for photodynamic therapy, J. Photochem. Photobiol., B 66 (2002) 89-106]. Recent reports have described carrier nanoparticles with additional active complementary and supplementary roles in PDT. We introduce a functional classification for nanoparticles in PDT to divide them into passive carriers and active participants in photosensitizer excitation. Active nanoparticles are distinguished from non-biodegradable carriers with extraneous functions, and sub-classified mechanistically into photosensitizer nanoparticles, [A.C. Samia, X. Chen, C. Burda, Semiconductor quantum dots for photodynamic therapy, J. Am. Chem. Soc. 125 (2003) 15736-15737, R. Bakalova, H. Ohba, Z. Zhelev, M. Ishikawa, Y. Baba, Quantum dots as photosensitizers? Nat. Biotechnol. 22 (2004) 1360-1361] self-illuminating nanoparticles [W. Chen, J. Zhang, Using nanoparticles to enable simultaneous radiation and photodynamic therapies for cancer treatment, J. Nanosci. Nanotechnology 6 (2006) 1159-1166] and upconverting nanoparticles [P. Zhang, W. Steelant, M. Kumar, M. Scholfield, Versatile photosensitizers for photodynamic therapy at infrared excitation, J. Am. Chem. Soc. 129 (2007) 4526-4527]. Although several challenges remain before they can be adopted for clinical use, these active or second-generation PDT nanoparticles probably offer the best hope for extending the reach of PDT to regions deep in the body.
authors.affiliation: Division of Bioengineering, National University of Singapore, 117574, Singapore.
authors.forename: Dev Kumar
authors.initials: DK
authors.lastname: Chatterjee
authors.forename: Li Shan
authors.initials: LS
authors.lastname: Fong
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000818:Animals; D003131:Combined Modality Therapy; D004337:Drug Carriers / Q000008:administration & dosage; D016503:Drug Delivery Systems; D006801:Humans; D053758:Nanoparticles / Q000145:classification; D009369:Neoplasms / Q000628:therapy*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage
chemical_list: D004337:Drug Carriers; D017319:Photosensitizing Agents